Design of Controlled Processing Conditions for Drop Forgings Made of Microalloy Steel Grades for Mining Industry

Abstract

Effect of plastic processing and controlled cooling on microstructure and mechanical properties of experimental steel grades with microalloyed with Ti, V and/or Nb, varying in the content of Mo is presented as an offer for mining industry for replacement traditionally heat-treatable hardenability grades. The goal of the work is producing microstructure condition, which after controlled hot forging and direct heat treatment, involving quenching and self-tempering, are meant to provide good combination of mechanical properties, such as TYS 800 MPa, UTS 1050 MPa, elongation to fracture at least A5 15% and/or impact strength at room temperature KCV 60 J/cm 2 . Hardenability assessment and dilatometric examination allowed formulation of direct heat treatment guidelines, taking into consideration fields of temperature and strain in a typical hot forging process, estimated numerically, with the use of plastometric tests results, as well as the use of unique cooling cycles after forging.On the basis of numerical analysis of thermomechanical parameters and temperature progression, hot forging and direct cooling conditions were selected to achieve assumed structural components, morphology and dispersion of both grain and precipitates. For established heat transfer model and experimentally plotted cooling curves numerical analysis of direct cooling, enabled by definition of characteristic points of austenite transformation and CCT diagrams was conducted. The modeling aided with dilatometric characterization enabled prediction of transformation products distribution. The formulated conclusions were verified in the experimental sampling of forging, evaluating the applicability of designed combinations of chemical composition and cooling cycle for selected forged part for mining industry.Keywords: microalloyed steel, thermomechanical processing, direct cooling, hammer forging, grain control Przedstawiono badania wpływu warunków odkształcania na gorąco i kontrolowanego chłodzenia na efektywność umocnienia eksperymentalnych stali z mikrododatkami Nb, Ti oraz V o zmiennej zawartości Mo. Pierwszym etapem pracy było zaprojektowanie składów chemicznych stali mikrostopowych, które po kontrolowanym kuciu na gorąco oraz obróbce cieplnej, polegającej na zahartowaniu i samoodpuszczeniu odkuwki bezpośrednio po kuciu, pozwolą na uzyskanie właściwości mechanicznych, tj.: granicy plastyczności 800 MPa, wytrzymałości na rozciąganie 1050 MPa, wydłużeniu A 5 15% i udarności w temperaturze otoczenia KCV 60 J/cm 2 . W oparciu o wyniki badań hartowności i analizę dylatometryczną opracowano wytyczne bezpośredniej obróbki cieplnej, uwzględniając obliczenia równowagi faz i wpływ temperatury na udział wydzieleń w wybranych wytopach oraz wyznaczone numerycznie pola temperatur dla typowego procesu kucia na gorąco, oparte o próby plastometryczne na symulatorze Gleeble 3800, oraz kontrolowane chłodzenie po kuciu.W oparciu numeryczną analizę parametrów termo-mechanicznych i zmian temperatury odkuwki modelowej dobrano warunki procesu kształtowania oraz sch...

Effect of direct cooling conditions on the microstructure and properties of hot-forged HSLA steels for mining applications

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Development of alternative technology of dual forming of profiled workpiece obtained by buckling

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Application of 3D Scanning as an Indirect Method to Analyze and Eliminate Errors on the Manufactured Yoke-Type Forgings Forged in SMED Device on Modernized Crank Press

“…[ 5 , 6 , 7 ]. For that reason, die forgings obtained on presses characterize in a much larger dimensional and shape precision as well as quality compared to forgings obtained on hammers [ 8 , 9 , 10 , 11 ]. In the case of die forging on mechanical presses, crank presses are those usually used, mostly owing to their high efficiency with a relatively high precision of the obtained forged products [ 12 ].…”